Structural Evolution of the Raft River Basin

Journal Article: Structural Evolution of the Raft River Basin

Abstract

Recent geological mapping, geophysical studies, and deep drilling in the Raft River area, Idaho, have yielded information that is not consistent with fault-block development of the Raft River basin. Paleozoic and lower Mesozoic allochthonous rocks that occur in the surrounding Sublett, Black Pine, Albion, and Raft River Mountains do not occur beneath the Cenozoic basin fill deposits of the Raft River Valley, nor do Cenozoic volcanic rocks that form the adjacent Cotterel and Jim Sage Mountains. Range-front faults have not been identified along the margins of ranges flanking the Raft River Valley. Normal faults found in the Cotterel and Jim Sage Mountains are inferred to be concave-upward extensional structures that involve only Tertiary volcanic rocks and basin-filling sediments. Concave-upward faults within the Raft River basin have been identified in seismic reflection profiles. Fault displacement of the basement rocks beneath the Raft River Valley has not been documented. Structural development of the Raft River basin based on gravity-induced tectonic denudation of nearby metamorphic core complexes is suggested.